Organic light-emitting diodes (OLEDs) are display devices which emit light by electrically excited fluorescent organic compound or by electrically excited phosphorescence organic compound. The organic light-emitting diodes have advantages of active luminescence, all-solid-state, wide visual angle, short response, etc, so it has an extensive application prospect in a field of display.
A conventional organic light-emitting diode comprises an anode, a cathode and a light emitting layer (EML) disposed between the anode and the cathode. In a case that the conventional organic light-emitting diode is driven by external voltage, holes injected from the anode and electrons injected from the cathode enter a recombination region of the EML to form excitons by recombination, and the excitons are subjected to radiative transition to emit photons, so as to achieve electroluminescence. However, because the mobility of the holes and the mobility of the electrons are different, the injection of the holes and the electrons is unbalanced, so that the actual luminous efficiency of the conventional organic light-emitting diode is low.